Gender-specific accuracy of lipid accumulation product index for the screening of metabolic syndrome in general adults: a meta-analysis and comparative analysis with other adiposity indicators

Background Lipid accumulation product (LAP) is a novel predictor index of central lipid accumulation associated with metabolic and cardiovascular diseases. This study aims to investigate the accuracy of LAP for the screening of metabolic syndrome (MetS) in general adult males and females and its comparison with other lipid-related indicators. Methods A systematic literature search was conducted in PubMed, Scopus, Web of Science, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and ProQuest for eligible studies up to May 8, 2024. Outcomes were pooled mean difference (MD), odds ratio (OR), and diagnostic accuracy parameters (sensitivity, specificity, and area under the summary receiver operating characteristic [AUSROC] curve). Comparative analysis was conducted using Z-test. Results Forty-three studies involving 202,313 participants (98,164 males and 104,149 females) were included. Pooled MD analysis showed that LAP was 45.92 (P < 0.001) and 41.70 units (P < 0.001) higher in men and women with MetS, respectively. LAP was also significantly associated with MetS, with pooled ORs of 1.07 (P < 0.001) in men and 1.08 (P < 0.001) in women. In men, LAP could detect MetS with a pooled sensitivity of 85% (95% CI: 82%–87%), specificity of 81% (95% CI: 80%–83%), and AUSROC curve of 0.88 (95% CI: 0.85–0.90), while in women, LAP had a sensitivity of 83% (95% CI: 80%–86%), specificity of 80% (95% CI: 78%–82%), and AUSROC curve of 0.88 (95% CI: 0.85–0.91). LAP had a significantly higher AUSROC curve (P < 0.05) for detecting MetS compared to body mass index (BMI), waist-to-height ratio (WHtR), waist-to-hip ratio (WHR), body roundness index (BRI), a body shape index (ABSI), body adiposity index (BAI), conicity index (CI) in both genders, and waist circumference (WC) and abdominal volume index (AVI) in females. Conclusion LAP may serve as a simple, cost-effective, and more accurate screening tool for MetS in general adult male and female populations. Supplementary Information The online version contains supplementary material available at 10.1186/s12944-024-02190-1.


METHODS
Eligibility criteria 5 Specify the inclusion and exclusion criteria for the review and how studies were grouped for the syntheses.Information sources 6 Specify all databases, registers, websites, organisations, reference lists and other sources searched or consulted to identify studies.Specify the date when each source was last searched or consulted.Page 6 Search strategy 7 Present the full search strategies for all databases, registers and websites, including any filters and limits used.Page 6 Selection process 8 Specify the methods used to decide whether a study met the inclusion criteria of the review, including how many reviewers screened each record and each report retrieved, whether they worked independently, and if applicable, details of automation tools used in the process.
Page 6 & Suppl.Table 2 Data collection process 9 Specify the methods used to collect data from reports, including how many reviewers collected data from each report, whether they worked independently, any processes for obtaining or confirming data from study investigators, and if applicable, details of automation tools used in the process.Page 7 Data items 10a List and define all outcomes for which data were sought.Specify whether all results that were compatible with each outcome domain in each study were sought (e.g. for all measures, time points, analyses), and if not, the methods used to decide which results to collect.10b List and define all other variables for which data were sought (e.g.participant and intervention characteristics, funding sources).Describe any assumptions made about any missing or unclear information.Study risk of bias assessment 11 Specify the methods used to assess risk of bias in the included studies, including details of the tool(s) used, how many reviewers assessed each study and whether they worked independently, and if applicable, details of automation tools used in the process.13d Describe any methods used to synthesize results and provide a rationale for the choice(s).If meta-analysis was performed, describe the model(s), method(s) to identify the presence and extent of statistical heterogeneity, and software package(s) used.13e Describe any methods used to explore possible causes of heterogeneity among study results (e.g.subgroup analysis, metaregression).Page 11 13f Describe any sensitivity analyses conducted to assess robustness of the synthesized results.Reporting bias assessment 14 Describe any methods used to assess risk of bias due to missing results in a synthesis (arising from reporting biases).N/A Certainty assessment 15 Describe any methods used to assess certainty (or confidence) in the body of evidence for an outcome.N/A

Study selection 16a
Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram.
Page 11-12 & Fig. 1 16b Cite studies that might appear to meet the inclusion criteria, but which were excluded, and explain why they were excluded.A consecutive or random sample of patients was enrolled.
It is unclear whether a consecutive or random sample of patients was enrolled.
There was no consecutive or random sample of patients enrolled.

#2 Was a case-control design avoided?
A case-control design was avoided.
It is unclear if a casecontrol design was avoided.
The study used a case-control design.

#3 Did the study avoid inappropriate exclusions?
There were no inappropriate exclusions of patients.
It is unclear if there were inappropriate exclusions of patients.
There were inappropriate exclusions of patients (e.g., patients with any physical and postural limitations precluding anthropometric measurements, patients with history of weight loss surgeries or any other procedures that caused WC reduction, such as liposuction, lipolysis, and abdominoplasty).

Index Test #4
Were the index test results interpreted without knowledge of the results of the reference standard?
This item was omitted since blinding LAP interpreter was considered to be irrelevant to the current study.LAP is an objective index test as it involves an objective measurement of TG using machine analyzers and a specific formula to obtain the final value.

#5
If a threshold was used, was it prespecified?
This item was omitted as the specific threshold of LAP for MetS has not been determined to date; hence, each study analyzed its own population optimal cut-off value.

#6
If a threshold was used, was the sample size included in the diagnostic analysis ≥ 300? a A threshold was used and the sample size included in the LAP accuracy analysis was ≥ 300.
It is unclear whether a threshold was used or the sample size included in the LAP accuracy analysis was ≥ 300.
A threshold was used and the sample size included in the LAP accuracy analysis was < 300.

#7 Was the calculation to determine the index test clearly described? b
The calculation including formula and units of LAP was clearly described.
One of the calculation components of LAP (formula or units) was not clearly described.
The calculation including formula and units of LAP was not clearly described.

#8 Were the methods used to determine the index test consistently applied across study subjects? b
The methods used to determine LAP were consistently applied across study subjects.
It is unclear if the methods used to determine LAP were consistently applied across study subjects.
The methods used to determine LAP were not consistently applied across study subjects.

Reference Standard #9
Is the reference standard likely to correctly classify the target condition?
The study used published and established criteria to define MetS.
It is unclear what criteria were used to define MetS.
The study did not use any published and established criteria to define MetS.

#10 Were the reference standard results interpreted without knowledge of the results of the index test?
This item was omitted as blinding the MetS diagnostic criteria interpreter was considered to be irrelevant to the current study.Since the threshold of LAP for MetS has not been determined to date, the MetS diagnostic criteria results would always be interpreted without the knowledge of the results of LAP.

#11 Was the reference standard and its definition clearly described? b
The type of MetS diagnostic criteria and all of the MetS components definitions were clearly described.
The type of MetS diagnostic criteria was clearly described without complete description of the MetS components.
Either the type of MetS diagnostic criteria or all of the MetS components definitions was not clearly described.

#12 Were the methods used to determine the reference standard consistently applied across study subjects? b
The methods used to determine MetS were consistently applied across study subjects.
It is unclear if the methods used to determine MetS were consistently applied across study subjects.
The methods used to determine MetS were not consistently applied across study subjects.

Flow and Timing #13 Was there an appropriate interval between index test(s) and reference standard?
There was an appropriate interval between the result collection of LAP and MetS.
It is not clear whether the interval between the result collection of LAP and MetS was appropriate.
There was no appropriate interval between the result collection of LAP and MetS.

Rationale 3 - 5 Objectives 4
Describe the rationale for the review in the context of existing knowledge.Page 4Provide an explicit statement of the objective(s) or question(s) the review addresses.Page 5

Table 3
Synthesis13a Describe the processes used to decide which studies were eligible for each synthesis (e.g.tabulating the study intervention

Table 2 .
[2]port25 Describe sources of financial or non-financial support for the review, and the role of the funders or sponsors in the review.Report which of the following are publicly available and where they can be found: template data collection forms; data extracted from included studies; data used for all analyses; analytic code; any other materials used in the review.PICO framework[2].AUC, area under curve; LAP, lipid accumulation product; MetS, metabolic syndrome; PICO, Population, Index Test, Comparator, and Outcome.
a Locations were based on the submitted manuscript file.N/A, not applicable or not available; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses.Supplementary

Table 4 .
Outcomes of the included studies.
[6]his additional item is formulated from a rule-of-thumb suggested by Bujang et al.[4], where a sample of minimum 300 subjects can often be considered sufficient in obtaining a reliable estimate of the sensitivity and specificity of most screening and diagnostic tests.bTheseadditionalitemsareadoptedand formulated from the QUADAS-2 signaling questions in McCrea et al.[5]and Munthali et al.[6].LAP, lipid accumulation product; MetS, metabolic syndrome; QUADAS-2, Quality Assessment of Diagnostic Accuracy Studies 2; WC, waist circumference.Supplementarya Data are presented in mean ± SD or median (IQR).b Authors that provided additional data on requests.AUC, area under curve; CI, confidence interval; FN, false negative; FP, false positive; IQR, interquartile range; LAP, lipid accumulation product; MetS, metabolic syndrome; N/A, not applicable or not available; OR, odds ratio; SD, standard deviation; Sn, sensitivity; Sp, specificity; TN, true negative; TP, true positive.AUSROC, area under the summary receiver operating characteristic; CI, confidence interval; LAP, lipid accumulation product; MetS, metabolic syndrome; Sn, sensitivity; Sp, specificity.